This invention relates to a combined caulking tube plunger and enclosure assembly, and, more particularly it relates to a unitary piece having a break-away plunger formed integrally with the enclosure portion.
Closures for caulking gun tubes are commonly formed in two pieces, including an outer rim which engages the end of the tube, and a separate plunger received in sealing relation to the rim, which plunger is engageable by the caulking gun ram to move through the tube. Such two part rim or ring plunger assemblies are relatively costly to make and use. First, they employ or require two manufacturing operations since the ring and plunger are made from separate parts, and there is commonly a waste area created by the manufacture of the ring or rim. Further, these parts must be separately inserted within or secured to the caulking tube.
See, for example, the patent of Perkins, U.S. Pat. No. 3,880,331, issued Apr. 29, 1975. In perkins there is disclosed a tube strengthening closure rim or ring in association with a plunger. However, the plunger and ring are associated together as separate parts and the plunger is initially frictionally gripped by the ring for movement away from the ring by compressed air applied to the plunger. The closure which is thus described in Perkins is a two-piece construction requiring separate manufacturing operations to create and form the ring as distint from the plunger.
Of course, one-piece plungers are known. An example of a cardboard tube employing a generally cup-shaped plunger is shown in Berg U.S. Pat. No. 3,319,841 issued May 16, 1967, in which a stamped cup of sheet metal forms the plunger. Berg does not disclose a plunger which also forms an integral rim which is crimped or which may be crimped to engage the lip or terminal end of the cardboard tube or container.
The patent of Sabaka No. 3,162,337, issued Dec. 22, 1964 shows another form of a caulking gun plunger which may be formed with a skirt having a depth in the range of 1/4 inch to 3/4 inches. Again, there is no disclosure or suggestion in Sabaka of incorporating such a plunger initially as an integral portion or part of a retainer or closure ring to effectively seal the cartridge prior to use. See also U.S. Pat. No. 3,211,347 to Phillips.
The problem with such one piece plungers is that they are generally not capable of long term protection of the fluid material in the caulking tube from spoilage (curing, drying, coagulating, etc.) due to air or moisture contact. The seal between the one-piece plunger and the wall of the tube while sufficient for the most part to prevent leakage of the fluid material from the containers, is not sufficient to prevent air and moisture contact over a period of time. In addition, temperature variations can lead to increased air an moisture exposure during storage of this type of caulking tube.
Accordingly, the need exists for a combined caulking tube plunger and enclosure which is capable of providing an air tight seal and yet easily separated to produce a break-away plunger, but which is easy to produce and apply to the caulking tube.